The story
From New Latin of the 19th century; by surface analysis, mycete + -oma; the fact that the word predates 20th century microbiology explains why the use of this name is not specific to mycotic disease: the disease was named for fungal and apparently fungal causes, and its full pathophysiology (and the current taxonomy of the various causative pathogens) was learned later.
Etymology from Wiktionary, CC BY-SA 4.0.